diff --git a/library/puppet b/library/puppet
index 51464ca..c26b96d 100644
--- a/library/puppet
+++ b/library/puppet
@@ -73,6 +73,7 @@ options:
     required: false
     default: stdout
     choices: [ 'stdout', 'syslog' ]
+    version_added: "2.1"
 requirements: [ puppet ]
 author: "Monty Taylor (@emonty)"
 '''
@@ -185,7 +186,7 @@ def main():
         if p['puppetmaster']:
             cmd += " --server %s" % pipes.quote(p['puppetmaster'])
         if p['show_diff']:
-            cmd += " --show-diff"
+            cmd += " --show_diff"
         if p['environment']:
             cmd += " --environment '%s'" % p['environment']
         if module.check_mode: